1. Field of the Invention
The present invention relates to an object levitating apparatus, which levitates an object in air (the term "levitate" here refers to the action of lifting an object so as to be in a floating state), an object transporting apparatus which uses said object levitating apparatus, and an object levitating bearing, along with an object levitating process and object transporting process.
2. Description of the Prior Art
The following systems are known in the prior art as examples of this type of apparatus.
(1) A system wherein an object is magnetically levitated and transported using an alternating current magnetic field flowing through a coil;
(2) A system wherein an object is levitated and transported using the Meissner effect of superconductivity; and,
(3) A system wherein an object is levitated and transported using pressurized air such as compressed air.
In the apparatuses described in (1) and (2) above, together with the object to be levitated and transported being limited to a ferromagnetic substance or semiconductor, these apparatuses also have the disadvantage of being unable to be applied to objects for which the placing under conditions of being subjected to magnetism is undesirable. In addition, with respect to the apparatus above which uses the Meissner effect of superconductivity, since an expensive coolant is required to cool a coil to an extremely low temperature, together with this leading to increased costs with respect to the consumption of this coolant, considerations also must be taken with respect to the safety of the coolant. Moreover, this apparatus also has the disadvantage of having to be made extremely large in size in order to levitate and transport objects for an extended period of time in a stable state.
On the other hand, in the apparatus described in (3) above, since a pressurized gas is required to be supplied to the entire surface of the object transport path, together with having to provide an elaborate pressurized gas supply device which thereby makes it difficult to reduce the size of the entire apparatus, this apparatus also suffers the disadvantage of encountering difficulty in controlling the pressure of the supplied gas so that it remains uniform over a wide range. In addition, in the case of using said apparatus under conditions in which the atmosphere must be kept clean, such as in a so-called "clean room", a device is required for suctioning and recovering any gas that escapes from the above-mentioned pressurized gas supply device to prevent diffusion of said escaped gas. In addition to this being an additional obstacle to reducing the size of the apparatus, this apparatus also has the disadvantage in that it is difficult to completely recover the gas.
However, an apparatus like that shown in FIG. 1 has recently been developed. Furthermore, this apparatus is disclosed on pages 745 and 746 of the "Lecture Collection of the Japan Acoustics Society" published on Oct. 3, 1983.
Namely, in FIG. 1, a standing wave (not shown) is produced between stepped circular diaphragm 2, vibrated by vibrating device 1, and correspondingly arranged reflecting plate 3, and a plurality of Styrofoam spheres 4 (weight: 1.2 mg, diameter: 4 mm) are levitated by a sound field. Furthermore, in FIG. 1, the direction of gravitational force is shown with arrow g. In this case, it has been verified that each of the spheres 4 is stationary in the air at an interval of 1/2 the wavelength of the ultrasonic waves, and their positions are at the valleys of sound pressure. In addition, the size of spheres able to be levitated is no more than 1/2 the wavelength, and their weight is considered to be related to sound pressure.
However, in this type of apparatus which uses a standing wave to make an object become stationary in the air at the locations of its nodes, the sphere 4 used for the test piece is currently limited to that which is extremely lightweight, and the vibration amplitude of diaphragm 2 must be made extremely large in order to levitate heavier and larger objects. Thus, in consideration of the stress-related destruction of diaphragm 2 and horn 1a (see FIG. 1), it would be difficult for this apparatus to stably levitate a heavy object for an extended period of time, thus making practical application of this apparatus far from attainable. In addition, although the use of a process in this constitution whereby sound waves are converged into powerful sound waves to allow levitation of relatively heavy objects can be considered, since sound waves would act on a small surface area in comparison with the diameter of diaphragm 2, the result would still be that the apparatus would still only be applicable to small objects.